PROPERTY-BASED INTEGRITY MONITORING OF OPERATING SYSTEM KERNELS

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Abstract

As the foundation of the trusted computing base, the operating system
kernel is a valuable target for attackers of a computer system
seeking maximum control and privilege. Furthermore, because the
majority of modern security solutions rely on the correctness of at
least some portion of the operating system kernel, skilled attackers
who successfully infiltrate kernel memory can remain undetected
indefinitely.
In this dissertation, we present an approach for detecting
attacks against the kernel's integrity (commonly referred to as
"rootkits"). Our approach, which we call
<em>property-based integrity monitoring</em>, works by monitoring and
analyzing the kernel's state at runtime. Unlike traditional security
solutions, our monitor operates in isolation of, and
independently from, the protected operating system and has direct
access to the kernel's runtime state.
The basic strategy behind property-based monitoring is to identify a
set of <em>properties</em> that are practical
to check, yet are effective at detecting the types of changes
an attacker might make - both known and yet-to-be-discovered. In
this work, we describe a practical and effective property for detecting
persistent control-flow modifications in running kernels, called
state-based control-flow integrity (SBCFI). Furthermore, to
address those data-only attacks that do not violate the kernel's
control-flow, we introduce a high-level policy language system for
enforcing <em>semantic integrity</em> constraints in runtime kernel data.
To evaluate the feasibility and effectiveness of our system, we have
implemented two property-based integrity monitors for the Linux
kernel - one using a virtual machine monitor and the other using a
PCI-based coprocessor. We demonstrate that property-based monitoring
is capable of detecting all publicly-available kernel integrity
threats while imposing less than 1% overhead on
the protected system. We conclude that property-based kernel integrity
monitoring can be both practical and effective.